Unhairing process



UNITED STATES PATENT OFFICE UNHAIRING PROCESS David Walker Jayne, Jr., Old Greenwich, Conn.,

assignor to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application December 10, 1938, Serial No. 244,933

7 Claims. (Cl. 1492) This invention relates to the unhairing of hides Although it is possible to prepare the guanidine and skins, which is a preliminary step in their sulfides as pure chemical compounds, and to add conversion into leather. More specifically, the them to the limeliquors or other alkaline unhairinvention relates to a new class of unhairing ing baths in this form, I have also found that accelerators for use in conjunction with aqueous good results are obtained by forming the guani- 5.

dispersions of alkaline hydrolyzing agents which dine sulfide (or, more accurately, the l yd e) have previously been used for unhairing purin the unhairing liquors themselves. This is poses. readily accomplished by adding such guanidine The conventional method of unhairing hides salts as guanidine carbonate, guanidine. sulfate and skins is to immerse them in a bath containand the like together w th w e s e inorganic 10 ing lime, sodium hydroxide or other alkaline sulfides such as sodium sulfide, ammonium sulfide, hydrolyzing agents, or in the case of sheepskins, calcium sulfide and the like. It will thus be seen to subject them to the action of these agents in that the invention in its broader aspects includes the form of an aqueous paste. It has been known any p oc s in w ich ides and S ins are 001 for many years that the addition to these baths tacted with an alkaline unhairing composition 15 of small amounts of water-soluble inorganic sulcontaining a guanidine Sulfide sulfhydrate, fides such as arsenic sulfide, sodium sulfide and W et e th SC pou p p Separately the like will speed up the unhairing action, and formed in situ.

accordingly these substances are known as un- The invention will be illustrated by the followhairing accelerators. ing examples to which, however, it is not limited. 20

More recent developments in the field of un- Example 1 hau'ing accelerators have suggested the replacemen]; of the inorganic sulfides by organic com.. lbs. Of Soaked. and trimmed. gOatSklnS were pounds hi might be expected to have mimer entered into a bath containing 10% of hydrated action on the hair and skin. One of the first of lime and 12% 0f guanidine Sulfide based on the 25 these was t discovery of McLaughlin based -weight of the skins. The skins were agitated in upon the examination of mellow limes, that certhe bath 15 minutes the m n nd 2 tain of the lower aliphatic amines such as diminutes in the evening of each d t bat methylamine would accelerate hair slippage when temperature Wits maintained t added to lime suspensions. This was followed by After 24 hours the long hair Was qu o e 30 th k of 'lurley and Windus, who Showed t and the skins were almost ready to be unhaired. aliphatic mercaptans or mercaptides would After 48 hours the skins unhaired easily on the crate as unhairing accelerators, but that organic unhairing machinesulfides and thiophenols are inactive for this pur- Example .2

pose' 3 packs of soaked and trimmed Persian goat- 35 I h l HOW dlscovered that sulfides 9 skins weighing 250 lbs. each were unhaired in gflamdme and alkyl or substltuted guam' baths having the followingcomposition based on dines are excellent unhairmg accelerators when the Weight of the skins used in unhairing baths or dispersions containing 40 an alkaline hydrolyzing agent such as lime or caustic soda. Guanidine is a strong organic base having the formula Bath No. 1 Bath No. 2 Bath No. 3 40 10% hydrated lime 10% hydrated lime 10% hydrated lime NH .75% guanidine ear- .6% guanidine car- 1% guanidine oarbonate bonate bonate H2NCNH: .75% calciumsulfide .6% calcium sulfide .75% calcium sulfide 1% soda ash 1% soda ash 1% soda ash A One or both of the hydrogen atoms of its amino groups can readily be substituted by alkyl or aryl The temperatures of the baths were Set at 4c hydrocarbon groups such as methyl ethyl propyl F. and the skins were entered and agitated for phenyl and the like, and I have discovered that 20 minutes in the morning and 3 minutes a night the sulfides of these hydrocarbon Substituted on the first working day. After 24 hours a defi- 50 guanid'ines e also good unhairing accelerators nite loosening of the skins of all three packs could Accordingly, it is understood that the te be noted with very little difference between them. guanidine as used in the appended claims is in- On the second working day the skins were tended to cover both guanidine itself and alkyl agitated in the bath for 3 minutes in the mornand aryl substituted guanidines. ing and 3 minutes at night. At the end of 48 u hours the best results were obtained in Bath No. 3; Bath N0. 1 was next while Bath No. 2 had some skins on which hair was still tight. Since the skins werefiaccid, /2% of soda ash was added to each bath and the skins were left until the third working day. 1

After '72 hours, the skins were well plumped by the added alkali. but the hair was quite loose. The formula of BathNo. 3 was best, and the skins from this bath were easily unhaired on the unhairing machine. Bath No. 2 contained several skins on which some of the hair was still tight.

The present application. specifically a method of unhairing of hides and skins in which a guanidine sulfide is formed in the unhairing bath by double decomposition between. guanidine. salts and inorganic sulfides including calcium sulfide. However I do not claim broadly unhairingprocesses in which calcium sulfideisernplovedv in conjunction with any organic base, as this. forms the subject matter of the copending application of Joseph G. Niederco'rn, Serial No. 244,935 filed concurrently herewith.

What I. claim is:

l'. Amethod of unhairing hides and skins which comprises contacting. them. with. an unhairing composition. comprising an alkaline hydrolyzing agent and a guanidine sulfide.

2'. A. method of. unhairihg hides and skins. which comprises immersing them in. an. aqueous dispersion. of an. alkaline: hydrolyzing. agent containing Bath N0. 1 was next, while as an unhairing accelerator a guanidine sulfide in solution. I

3.. A method of unhairing hides and skins which comprises immersing them in an aqueous dispersion of an alkaline hydrolyzing agent to which has been added a salt of a guanidine together with an inorganic sulfide capable of reacting therewith toproduce a gu'anidine sulfide in solution.

4. A method of unhairing hides and skins which comprises immersing them in an aqueous dispersion of an alkaline hydrolyzing agent to which has been added a salt of a gether with calcium sulfide.

5. A method: or unhairing hides and skins.

which comprisesimmersing them in an aqueous dispersion. of an alkaline hydrolyzing agent to which has been added a salt of a guanidine together with calcium sulfide in amounts of to of the guam'dine salt.

6.. A- method .of unhairing hides and skins which comprises immersing. them in an aqueous guanidine to- 

